Photolithography technology has so far generally been employed in a fine processing upon manufacturing electronic parts such as a semiconductor and so on, a three-dimensional fine structured article and the like. In a photolithography method, a positive-working or negative-working radiation sensitive resin composition is used to form a resist pattern. Among these radiation sensitive resin compositions, a radiation sensitive resin composition comprising, for example, an alkali-soluble resin and a quinone diazide compound which is a photosensitive substance is widely being used as a positive-working photoresist.
By the way, in recent years, along with the tendencies which induce high degree of integration and high process speed of LSI, fining of the design rule is being required such as a quarter-micron or further finer in the field of manufacturing microelectronic devises. In order to respond to further fining of a design rule, light sources so far applied such as a visible light or a near-ultraviolet light (wavelength; 400 to 300 nm) and so on are not enough as a light-exposure source. Therefore it is getting necessary to use a deep ultraviolet ray such as KrF excimer laser (248 nm), ArF excimer laser (193 nm) and so on or further shorter wavelength radiation such as X-rays and electron beams, and then a lithographic process using these light sources has been proposed and has been coming into practice. In order to respond to the further fining of this design rule, higher resolution is also being required for a radiation sensitive resin composition that is used as a photoresist upon fine processing. Further, besides high resolution, an improvement of performance such as sensitivity and accuracy of image dimension are being required to a radiation sensitive resin composition in the same time. In order to respond it, “a chemically amplified radiation sensitive resin composition” was proposed as a radiation sensitive resin composition having a high resolution and being sensitive to the radiation with short wavelength. This chemically amplified radiation sensitive resin composition contains a compound that generates an acid by irradiation of radiation and is advantageous in obtaining a high sensitivity by an image-formation step brought by the catalytic action of the acid generated from this acid generating compound by irradiation of radiation. Therefore the chemically amplified radiation sensitive resin composition is taking the place of the radiation sensitive resin composition so far applied and is prevailing.
However, a pattern formation with a KrF excimer laser (248 nm) has not been catching up with a fine pattern size currently being required and there is a situation that a process by an ArF excimer laser (193 nm) has not yet been coming into practice. In this connection, a fine resist pattern forming method as follows is being proposed. That is, first a resist pattern is formed by use of a chemically amplified resist according to a pattern forming process with a KrF excimer laser. Next a water-soluble resin film is formed over the resist pattern by applying on the resist pattern an auxiliary for a fine pattern formation that is a water-soluble resin composition to be crosslinked or cured by an acid. The resist pattern and the auxiliary are full-exposed without a mask and/or heated and an acid is made diffused from the resist pattern into the water-soluble resin film, thereby the water-soluble resin film is crosslinked or cured to be made insoluble in a developer. Thereafter uncured area is removed by a development to thicken the resist pattern, eventually to narrow widths between resist patterns, and thereby a fining of a resist pattern is realized and a fine resist pattern below a resolution limit of a light-exposure wavelength is practically and effectively formed (see, for example, Japanese laid-open Patent Publication Nos. Hei 5-241348, Hei 6-250379 and Hei 10-73927.).
This method is being paid attention as a useful method since it is not required to invest facilities of a high price such as a light-exposure device for a short wavelength and is possible to reduce a dimension of a space area of a resist pattern effectively. This auxiliary for a fine pattern formation comprising a water-soluble resin composition applied for a formation of a fine pattern has been already placed on the market such as RELACS series (manufactured by Clariant Japan K.K.), for example.
The aforementioned auxiliary contains a modified polyvinyl alcohol which is water- or alkali-soluble and is protected with a protecting group (hereafter simply called “modified polyvinyl alcohol” sometimes) as a component. On the other hand, it is known that polyvinyl alcohol generates an associated body by a hydrogen bond. This associated body is a kind of a high molecular gel and may be regarded as a body to be swollen with a solvent having a three dimensional network structure, in which the system is all over connected by a hydrogen bond. And polyvinyl alcohol is a crystalline polymer, and a crosslinked point thereof is thought to be an entangled point trapped among micro crystallites. This associated body is very tough in an aqueous solution, might cause defects such as a reduction of filtration speed upon using a filter of a size of 0.1 μm or less and so on, and a problem to be a cause of a foreign matter in an applied film. Furthermore, this associated body has a problem of stability with time that it is likely to be formed again even after the associated body is once removed.
The modified polyvinyl alcohol which is used as a raw material of an auxiliary for fine pattern formation contains a high molecular weight body component based on the association in the same way as a polyvinyl alcohol, and has problems in a filtration property and stability with time. Therefore the auxiliary for fine pattern formation which was prepared by using this modified polyvinyl alcohol has the same problems as polyvinyl alcohol described above. Furthermore, concerning the auxiliary for fine pattern formation which was prepared by using this modified polyvinyl alcohol, there is another problem that an application defect takes place upon applying it on a substrate. In addition, there is further problem of a development defect in a pattern based on residue of an unnecessary auxiliary for fine pattern formation, which is not removed upon removal of the uncured auxiliary for fine pattern formation by development after applying the auxiliary for fine pattern formation on the resist pattern and then exposing it to light, followed by heating and so on, and remained on the resist pattern.
Accordingly an object of the present invention is to offer an auxiliary for fine pattern formation on which the above-described problems are solved, namely which is good in a filtration property, has less number of application defects and development defects, is good in stability with time and can be used for a manufacture of a semiconductor.
Another object of the present invention is to offer a modified polyvinyl alcohol which is used as a constitutional material in the above-described auxiliary for fine pattern formation and is excellent in filterability and stability with time, and the production method thereof.